Solar panel

ABSTRACT

A high efficiency configuration for a solar cell module comprises solar cells arranged in an overlapping shingled manner and conductively bonded to each other in their overlapping regions to form super cells, which may be arranged to efficiently use the area of the solar module.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/540,372 titled “Solar Panel” filed Aug. 14, 2019, which claimspriority to U.S. patent application Ser. No. 15/441,117 titled “SolarPanel” filed Feb. 23, 2017 (now U.S. Pat. No. 10,510,907 B2), whichclaims benefit of priority to U.S. Provisional Patent Application62/299,287 titled “Solar Panel” filed February 24, 2016. Each of aboveapplications is incorporated herein by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under DE-EE0007190awarded by The U.S. Department of Energy. The government has certainrights in the invention.

FIELD OF THE INVENTION

The invention relates generally to solar cell modules in which the solarcells are arranged in a shingled manner.

BACKGROUND

Alternate sources of energy are needed to satisfy ever increasingworld-wide energy demands. Solar energy resources are sufficient in manygeographical regions to satisfy such demands, in part, by provision ofelectric power generated with solar (e.g., photovoltaic) cells.

SUMMARY

In a first aspect, a solar cell comprises a silicon semiconductor diodestructure having a front surface to be illuminated by light and a backsurface, a front surface metallization pattern comprising a plurality ofstraight front surface bus bars each having a long axis, and a rearsurface metallization pattern comprising a plurality of straight rearsurface bus bars each having a long axis. The front surface bus bars arearranged side-by-side with their long axes parallel and spaced apartfrom each other in a direction perpendicular to their long axes. Therear surface bus bars are arranged side-by-side with their long axesparallel and spaced apart from each other in a direction perpendicularto their long axes. The long axes of the rear surface bus bars areoriented parallel to the long axes of the front surface bus bars, andeach front surface bus bar partially overlies a corresponding rearsurface bus bar to overlap the corresponding rear surface bus bar in adirection perpendicular to the long axes of the front and rear surfacebus bars.

The front and rear surfaces of the solar cell may be square orpseudo-square in shape, for example. The long axes of the front and rearsurface bus bars may be oriented parallel to an edge of the solar cell,and may extend for substantially the full length of the edge of thesolar cell.

The solar cell may comprise one or more additional front surface busbars each having a long axis oriented parallel to the long axes of theplurality of front surface bus bars, arranged side-by-side with theplurality of front surface bus bars and spaced apart from each other andfrom the plurality of front surface bus bars in a directionperpendicular to their long axes, and not overlying any rear surface busbar.

The solar cell may comprise one or more additional rear surface bus barseach having a long axis oriented parallel to the long axes of theplurality of rear surface bus bars, arranged side-by-side with theplurality of rear surface bus bars and spaced apart from each other andfrom the plurality of rear surface bus bars in a direction perpendicularto their long axes, and not underlying any front surface bus bar.

In a second aspect, a method of manufacturing a silicon solar cellcomprises providing a silicon semiconductor diode structure having afront surface to be illuminated by light and a back surface, depositingon the front surface a front surface metallization pattern comprising aplurality of straight front surface bus bars each having a long axis,and depositing on the rear surface a rear surface metallization patterncomprising a plurality of straight rear surface bus bars each having along axis. The front surface bus bars are arranged side-by-side withtheir long axes parallel and spaced apart from each other in a directionperpendicular to their long axes. The rear surface bus bars are arrangedside-by-side with their long axes parallel and spaced apart from eachother in a direction perpendicular to their long axes. The long axes ofthe rear surface bus bars are oriented parallel to the long axes of thefront surface bus bars, and each front surface bus bar partiallyoverlies a corresponding rear surface bus bar to overlap thecorresponding rear surface bus bar in a direction perpendicular to thelong axes of the front and rear surface bus bars.

The method may comprise depositing on the front surface one or moreadditional front surface bus bars each having a long axis orientedparallel to the long axes of the plurality of front surface bus bars,arranged side-by-side with the plurality of front surface bus bars andspaced apart from each other and from the plurality of front surface busbars in a direction perpendicular to their long axes, and not overlyingany rear surface bus bar.

The method may comprise depositing on the rear surface one or moreadditional rear surface bus bars each having a long axis orientedparallel to the long axes of the plurality of rear surface bus bars,arranged side-by-side with the plurality of rear surface bus bars andspaced apart from each other and from the plurality of rear surface busbars in a direction perpendicular to their long axes, and not underlyingany front surface bus bar.

In a third aspect, a method of making a shingled string of solar cellscomprises obtaining a solar cell as described in the first aspect aboveand/or as manufactured by the second aspect above, identifying thelocation of each of the front surface bus bars with a camera, andcutting a plurality of scribe lines in the solar cell on the rear of thesolar cell. Each scribe line is cut parallel to and through acorresponding rear surface bus bar into the silicon semiconductorstructure at a location referenced to the location determined with thecamera of the front surface bus bar partially overlying the rear surfacebus bar, with the scribe line spaced apart from an edge of the frontsurface bus bar by a predetermined distance.

The method may further comprise separating the solar cell along thescribe lines to form a plurality of smaller solar cells each of whichcomprises a front surface bus bar on its front surface positioned alonga first edge of the smaller solar cell and a rear surface bus bar on itsrear surface positioned along a second edge of the smaller solar cellopposite from its first edge, and arranging the plurality of smallersolar cells in line with front and rear surface bus bars of adjacentsmaller solar cells overlapping in a shingled manner and conductivelybonded to each other to electrically and mechanically connect thesmaller solar cells in series.

These and other embodiments, features and advantages of the presentinvention will become more apparent to those skilled in the art whentaken with reference to the following more detailed description of theinvention in conjunction with the accompanying drawings that are firstbriefly described.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-sectional diagram of a string of series-connectedsolar cells arranged in a shingled manner with the ends of adjacentsolar cells overlapping to form a shingled super cell.

FIG. 2 shows a diagram of the front surface of an example rectangularsolar module comprising a plurality of rectangular shingled super cells,with the long side of each super cell having a length of approximatelythe full length of the long side of the module. The super cells arearranged with their long sides parallel to the long sides of the module.

FIGS. 3A-3C show steps in a conventional process for separating astandard size silicon solar cell wafer into smaller silicon solar cellsto be arranged in a shingled string of solar cells.

FIGS. 4A-4C show steps in an improved process for separating a standardsize silicon solar cell wafer into smaller silicon solar cells to bearranged in a shingled string of solar cells.

FIGS. 5A-5B show an example front surface metallization pattern for astandard size silicon solar cell suitable for use in the method of FIGS.4A-4C.

FIGS. 6A-6B show an example rear surface metallization pattern for astandard size silicon solar cell suitable for use with the front surfacemetallization pattern of FIGS. 5A-5B in the method of FIGS. 4A-4C.

FIGS. 7A-7B show another example front surface metallization pattern fora standard size silicon solar cell suitable for use in the method ofFIGS. 4A-4C.

FIGS. 8A-8B show an example rear surface metallization pattern for astandard size silicon solar cell suitable for use with the front surfacemetallization pattern of FIGS. 7A-7B in the method of FIGS. 4A-4C.

FIG. 9 shows the locations at which scribe lines are to be cut on theexample rear surface metallization pattern of FIGS. 8A-8B.

FIG. 10A and FIG. 10B show, respectively, front and rear surfacemetallization patterns on a separated solar cell prepared by the methodof FIGS. 4A-4C using the front and rear surface metallization patternsof FIGS. 7A-7B and FIGS. 8A-8B.

FIG. 11A and FIG. 11B show another example front surface metallizationpattern for a standard size silicon solar cell suitable for use in themethod of FIGS. 4A-4C. In this example the metallization patterncomprises fiducials.

DETAILED DESCRIPTION

The following detailed description should be read with reference to thedrawings, in which identical reference numbers refer to like elementsthroughout the different figures. The drawings, which are notnecessarily to scale, depict selective embodiments and are not intendedto limit the scope of the invention. The detailed descriptionillustrates by way of example, not by way of limitation, the principlesof the invention. This description will clearly enable one skilled inthe art to make and use the invention, and describes severalembodiments, adaptations, variations, alternatives and uses of theinvention, including what is presently believed to be the best mode ofcarrying out the invention.

As used in this specification and the appended claims, the singularforms “a,” “an,” and “the” include plural referents unless the contextclearly indicates otherwise. Also, the term “parallel” is intended tomean “substantially parallel” and to encompass minor deviations fromparallel geometries. The term “perpendicular” is intended to mean“perpendicular or substantially perpendicular” and to encompass minordeviations from perpendicular geometries rather than to require that anyperpendicular arrangement described herein be exactly perpendicular. Theterm “square” is intended to mean “square or substantially square” andto encompass minor deviations from square shapes, for examplesubstantially square shapes having chamfered (e.g., rounded or otherwisetruncated) corners. The term “rectangular” is intended to mean“rectangular or substantially rectangular” and to encompass minordeviations from rectangular shapes, for example substantiallyrectangular shapes having chamfered (e.g., rounded or otherwisetruncated) corners. The term “identical” is intended to mean “identicalor substantially identical” and to encompass minor deviations in shape,dimensions, structure, composition, or configuration, for example.

This specification discloses high-efficiency solar modules (alsoreferred to herein as solar panels) comprising silicon solar cellsarranged in an overlapping shingled manner and electrically connected inseries by conductive bonds between adjacent overlapping solar cells toform super cells, with the super cells arranged in physically parallelrows in the solar module. A super cell may comprise any suitable numberof solar cells. The super cells may have lengths spanning essentiallythe full length or width of the solar module, for example, or two ormore super cells may be arranged end-to-end in a row. This arrangementhides solar cell-to-solar cell electrical interconnections and increasesthe efficiency and the aesthetic attractiveness of the module.

As explained in more detail below, this specification further disclosesfront and rear surface metallization patterns for standard size siliconsolar cell wafers that are to be separated into smaller (e.g.,rectangular strip) solar cells for use in forming shingled arrangementsof solar cells (super cells) as described above. These front and rearsurface metallization patterns allow the standard size solar cells to beseparated into smaller cells by a method resulting in greater precisionin the location of edges of the smaller solar cells with respect tofront and rear surface metallization features (e.g., bus bars). Thismethod is also elaborated on below. The improved precision in thelocation of front and rear surface metallization features on theseparated solar cells reduces the amount of overlap between adjacentsolar cells in a super cell required to form a good electricalconnection between the solar cells.

Turning now to the figures for a more detailed understanding of thesolar cells, solar modules, and methods described in this specification,FIG. 1 shows a cross-sectional view of a string of series-connectedsolar cells 10 arranged in a shingled manner with the ends of adjacentsolar cells overlapping and electrically connected to form a super cell100. Each solar cell 10 comprises a semiconductor diode structure andelectrical contacts to the semiconductor diode structure by whichelectric current generated in solar cell 10 when it is illuminated bylight may be provided to an external load.

In the examples described in this specification, each solar cell 10 is arectangular crystalline silicon solar cell having front (sun side)surface and rear (shaded side) surface metallization patterns providingelectrical contact to opposite sides of an n-p junction, the frontsurface metallization pattern is disposed on a semiconductor layer ofn-type conductivity, and the rear surface metallization pattern isdisposed on a semiconductor layer of p-type conductivity. However, othermaterial systems, diode structures, physical dimensions, or electricalcontact arrangements may be used if suitable. For example, the front(sun side) surface metallization pattern may be disposed on asemiconductor layer of p-type conductivity, and the rear (shaded side)surface metallization pattern disposed on a semiconductor layer ofn-type conductivity.

Rectangular solar cells 10 may be prepared, for example, by separating astandard size square or pseudo-square solar cell wafer into two or more(i.e., N) rectangular solar cells each having a length equal to the sidelength (e.g., 156 millimeters) of the standard sized solar cell waferand a width equal to a fraction (i.e., about 1/N) of the side length ofthe standard sized solar cell wafer. N may be, for example, 2 to 20 ormore, for example 6 or 8.

Solar cells 10 may also be prepared, for example, by separating astandard size square or pseudo-square solar cell wafer along a first setof N-1 (e.g., cleave) lines parallel to one side of the wafer and alonga second set of P-1 lines oriented perpendicular to the first set oflines to form N×P solar cells having widths of about 1/N of the sidelength of the standard size wafer and lengths of about 1/P of the sidelength of the standard size wafer. For example, for N=6 and P=2 astandard size wafer having side lengths of 156 millimeters would provide12 rectangular solar cells 10 each having a width of about 26millimeters and a length of about 78 millimeters.

Referring again to FIG. 1, in super cell 100 adjacent solar cells 10 areconductively bonded to each other in the region in which they overlap byan electrically conductive bonding material 12 that electricallyconnects the front surface metallization pattern of one cell to the rearsurface metallization pattern of the adjacent cell. Suitableelectrically conductive bonding materials may include, for example,electrically conductive adhesives and electrically conductive adhesivefilms and adhesive tapes, and conventional solders.

A terminal lead 15 (e.g., a metal ribbon) is conductively bonded to asolar cell 10 at one end of super cell 100 to provide an electricaloutput of one polarity (either positive or negative) from the supercell, and another terminal lead 15 is conductively bonded to the solarcell 10 at the other end of the super cell to provide a secondelectrical output from the super cell of the opposite polarity. In theillustrated example one terminal lead is bonded to the rear surfacemetallization its solar cell and the other terminal lead is bonded tothe front surface metallization of its solar cell, and all solar cellsin the super cell contribute power to its output. In an alternativevariation, not shown, both terminal leads are bonded to the rear surfacemetallization of their solar cells, and one of the end solar cells doesnot contribute power to the output of the super cell. The lattervariation may simplify lay-up of a solar module during the manufacturingprocess.

Still referring to FIG. 1, one or more additional conductive leads(e.g., metal ribbons) 17 may each be conductively bonded to the rearsurface metallization of a corresponding solar cell located at anintermediate position between the ends of the super cell. Leads 17 maybe used, for example, to create bypass diode circuits around segments ofthe super cell.

FIG. 2 shows a front view of an example rectangular solar module 200comprising six rectangular super cells 100, each of which has a lengthapproximately equal to the length of the long sides of the solar module.In this example the super cells are arranged as six parallel rows withtheir long sides oriented parallel to the long sides of the module. Asimilarly configured solar module may include more or fewer rows of suchside-length super cells than shown in this example. In other variationsthe super cells may each have a length approximately equal to the lengthof a short side of a rectangular solar module, and be arranged inparallel rows with their long sides oriented parallel to the short sidesof the module. In yet other arrangements each row may comprise two ormore super cells, which may be electrically interconnected in series forexample. The modules may have short sides having a length, for example,of about 1 meter and long sides having a length, for example, of about1.5 to about 2.0 meters. Any other suitable shapes (e.g., square) anddimensions for the solar modules may also be used. A super cell maycomprise any suitable number of rectangular solar cells of any suitabledimensions. Similarly, a row of super cells may comprise any suitablenumber of rectangular solar cells of any suitable dimensions arranged inone or more super cells.

Solar modules as described herein typically comprise many more (e.g., Ntimes) as many solar cells as a conventional module of the same sizebecause N rectangular solar cells are formed from a single conventionalsized solar cell wafer. Optionally, the super cells formed from thesesolar cells may be arranged in an electrically parallel/seriescombination that provides current and voltage outputs similar to thoseprovided by a solar module of about the same size comprisingseries-connected conventional size solar cells. For example, if aconventional module includes M conventional size solar cellselectrically connected in series, then a corresponding shingled supercell module comprising N electrically parallel rows of super cells witheach super cell row comprising M series connected rectangular solarcells (each having 1/N the area of a conventional solar cell) wouldprovide about the same voltage and current output as the conventionalmodule.

Any other suitable series, parallel, or series and parallel electricalinterconnection of the super cells in a solar module may also be used.

Referring now to FIGS. 3A-3C, in one conventional process for separatinga standard size silicon solar cell wafer 305 into smaller silicon solarcells 310 to be arranged in a shingled string of solar cells, the solarcell wafer 305 comprises pairs of front surface bus bars 320 and rearsurface bus bars 330 oriented parallel to each other and spaced apartfrom each other along the plane of the solar cell wafer by a distanceD1±delta1. A camera system 335 identifies the location of the edge ofrear bus bar 330 nearest to the front surface bus bar, and a laser cutsa scribe line in the rear surface of the solar cell wafer parallel tothe rear surface bus bar, between the rear surface bus bar and the frontsurface bus bar, at a distance D2±delta2 from the edge of the rearsurface bus bar identified by the camera system. Two or more such scribelines are cut in the rear surface of the solar cell wafer by this method(each scribe line between a different pair of front and rear surface busbars), and then the solar cell wafer is separated (e.g., cleaved) alongthe scribe lines to form silicon solar cells 310.

As shown in the example of FIG. 3B, each such silicon solar cell 310comprises a rear surface bus bar 330 oriented parallel to a firstcleaved edge of the solar cell and spaced apart from that edge by adistance D2±delta2, and a front surface bus bar 320 oriented parallel toa second cleaved edge of the solar cell, opposite from the first cleavededge, and spaced apart from the second cleaved edge by a distanceD3±delta3 (where D3=D1−D2 and delta3=delta1+delta2). In some variations,D1=0.5 millimeters (mm), D2=0.3 mm, D3=0.2 mm, delta1=0.5 mm,delta2=0.15 mm, and delta3=0.66 mm.

Referring now to FIG. 3C, two such silicon solar cells 310 may bearranged with the front bus bar 320 of one of the solar cells orientedparallel to, overlapped by, and conductively bonded to the rear surfacebus bar 330 on another solar cell. This pattern may be continued tobuild a shingled super cell as shown in FIG. 1, for example. Generally,it is preferred that the front and rear surface bus bars of adjacentsolar cells overlap by a minimum distance L1. In some variations, L1=0.5mm.

The amount by which two adjacent solar cells 310 must overlap to ensurethat their bus bars overlap by at least L1 depends on the magnitudes ofD1, D2, and their variations. In the worst case, to achieve a minimumbus bar overlap of Ll solar cells prepared by the method just describedmust overlap by a distance L2=D3+delta3+L1+D2+delta2. The worst casevalue for L2 may for example be greater than or equal to 1.8 mm forsolar cells 310 prepared by the method just described. This value for L2may be undesirably large, because it reduces exposed active area of thesolar cells, and may lead to undesirably narrow process windows (e.g.,requirements for high precision) for subsequent steps in assembling ashingled string of such solar cells.

Referring now to FIGS. 4A-4C, in an improved process for separating astandard size silicon solar cell wafer 405 into smaller silicon solarcells 410 to be arranged in a shingled string of solar cells, the solarcell wafer 405 comprises pairs of front surface bus bars 420 and rearsurface bus bars 430 oriented parallel to each other with the rearsurface bus bar partially underlying the front surface bus bar so thatthe pair of bus bars overlaps by a distance D4±delta4 in a directionperpendicular to the long axes of the bus bars. A camera system 435identifies the location of the edge of front bus bar 420 nearest to therear surface bus bar, and a laser cuts a scribe line in the rear surfaceof the solar cell wafer through the rear surface bus bar at a distanceD5±delta5 from the edge of the front surface bus bar identified by thecamera system. Two or more such scribe lines are cut in the rear surfaceof the solar cell wafer by this method (each scribe line through adifferent rear surface bus bar), and then the solar cell wafer isseparated (e.g., cleaved) along the scribe lines to form silicon solarcells 410.

As shown in the example of FIG. 4B, each such silicon solar cell 410comprises a rear surface bus bar 430 oriented parallel to and directlyabutting a first cleaved edge of the solar cell, and a front surface busbar 420 oriented parallel to a second cleaved edge of the solar cell,opposite from the first cleaved edge, and spaced apart from the secondcleaved edge by the distance D5±delta5. In addition, each silicon solarcell 410 may also comprise a residual bus bar portion 435 cut from therear surface bus bar ultimately located on another silicon solar cell410 separated from an adjacent portion of silicon solar cell wafer 405.Residual bus bar portion 435 typically does not form a part of anydesired electric circuit, and may optionally be removed from solar cells410. Residual bus bar portion 435 has a width D6±delta6 (where D6=D4+D5and delta6=delta4+deltat5). In some variations, D4=0.5 mm, delta4=0.5mm, D5=0.2 mm, and delta5=0.1 mm. More generally, D5 may for example beabout 0.2 mm to about 0.5 mm.

Referring now to FIG. 4C, two such silicon solar cells 410 may bearranged with the front bus bar 420 of one of the solar cells orientedparallel to, overlapped by, and conductively bonded to the rear surfacebus bar 430 on another solar cell. This pattern may be continued tobuild a shingled super cell as shown in FIG. 1, for example. Generally,it is preferred that the front and rear surface bus bars of adjacentsolar cells overlap by a minimum distance L1. In some variations, L1=0.5mm.

In the worst case, to achieve a minimum bus bar overlap of L1 solarcells prepared by the improved method just described must overlap by adistance L2=L1+D5+delta5. The worst case value for L2 may for example beless than or equal to 0.9 mm for solar cells 410 prepared by theimproved method just described. This is a significant reduction inrequired overlap, compared to the method of FIGS. 3A-3C, advantageouslyincreases the amount of exposed active area of the solar cells, and mayresult in desirably broadened process windows (e.g., reduced precisionrequirements) for subsequent steps in assembling a shingled string ofsuch solar cells. The improved method just described may also reduce theprecision with which the front and rear surface bus bars must bedeposited on the standard size solar cell wafer.

Referring now to FIGS. 5A-5B, an example front surface metallizationpattern for a standard sized silicon solar cell suitable for use in themethod of FIGS. 4A-4C comprises a plurality of straight front surfacebus bars arranged side-by-side with their long axes parallel. The frontsurface bus bars are spaced apart from each other in a directionperpendicular to their long axes. In the illustrated example each frontsurface bus bar 420 comprises a plurality of contact pads 420P spacedapart along the axis of the bus bar and interconnected by a conductiveline. Any other suitable configuration for a front surface bus bar mayalso be used. Each bus bar is physically and electrically connected to acorresponding plurality of conductive fingers 440 orientedperpendicularly to the bus bar to form a comb-like conductive structure.Conductive fingers 440 collect current from throughout the front surfaceof a separated solar cell 410.

Referring now to FIGS. 6A-6B, an example rear surface metallizationpattern suitable for use with the front surface metallization pattern ofFIGS. 5A-5B (in the method of FIGS. 4A-4C) comprises a plurality ofstraight rear surface bus bars 430 arranged side-by-side with their longaxes parallel and spaced apart from each other in a directionperpendicular to their long axes. In the illustrated example, ratherthan being a continuous structure each bus bar 430 is formed as aplurality of discrete contact pads 430P arranged in line and spacedapart along the bus bar axis. Any other suitable configuration for arear surface bus bar may also be used. The example rear surfacemetallization pattern of FIGS. 6A-6B also comprises contact pads 450 anda rear surface contact 455. In an assembled solar module, contact pads450 may, for example, be bonded to conductive leads (e.g., leads 15 or17 described above) used to form bypass diode circuits or to draw powerfrom the solar cells. Rear surface bus bars 430 and contact pads 450 arephysically and electrically connected to rear surface contact 455, whichcollects current from throughout the rear surface of a separated solarcell 410.

FIG. 6B also indicates with (imaginary) line 470 where a scribe line maybe cut in the rear surface metallization through a bus bar 430, asdescribed above with respect to FIGS. 4A-4C.

Front surface bus bar contact pads 420P (FIGS. 5A-5B) and rear surfacebus bar contact pads 430P (FIGS. 6A-6C) are dimensioned and positionedso that when separated solar cells 410 are positioned in an overlappingmanner as shown in FIG. 4C, corresponding front surface and rear surfacecontact pads on the overlapping solar cells may be aligned along thedirection of the bus bar axes as well as along the direction of solarcell overlap.

Referring again to FIG. 6A, the central bus bar 430 in this example rearsurface metallization pattern (comprising contact pads 430P that arewider than those in the other rear surface bus bars) does not underlieany front surface bus bar. Each of the other rear surface bus bars 430partially underlies a corresponding front surface bus bar. Referringagain to FIG. 5A, the two front surface bus bars 420 located alongopposite edges of the standard size solar cell do not overlie any rearsurface bus bar. Each of the other front surface bus bars 420 partiallyoverlies a corresponding rear surface bus bar.

FIGS. 7A-7B show another example front surface metallization pattern fora standard sized silicon solar cell suitable for use in the method ofFIGS. 4A-4C, differing from that of FIGS. 5A-5B primarily in thatcontact pads 420P vary in size along the front surface bus bar. In theillustrated example, each front surface bus bar comprises three contactpads 420P of a first size, one at each end and one in the middle, andadditional contact pads of a second smaller size evenly spaced along thebus bar between the larger contact pads.

FIGS. 8A-8B show an example rear surface metallization pattern suitablefor use with the front surface metallization pattern of FIGS. 7A-7B inthe method of FIGS. 4A-4C, differing from that of FIGS. 6A-6B primarilyin that contact pads 430P vary in size in a manner similar to andcorresponding to that of contact pads 420P in FIGS. 7A-7B.

In FIG. 9, imaginary lines 470 indicate where scribe lines may be cutthrough rear surface bus bars 430 in the example rear surfacemetallization pattern of FIG. 8B, as described above with respect toFIGS. 4A-4C.

FIG. 10A shows the front surface metallization pattern on a solar cell410 prepared by the method of FIGS. 4A-4C using the front and rearsurface metallization patterns of FIGS. 7A-7B and FIGS. 8A-8B. FIG. 10Bshows the rear surface metallization patterns on the solar cell.

A front surface metallization pattern suitable for use in the method ofFIGS. 4A-4C may comprise fiducial markers located at predetermined andknown locations in the metallization pattern. The camera system used inthe method may use the fiducials as reference points by which toprecisely identify the locations of other features in the metallizationpattern such as front surface bus bars, for example. In the frontsurface metallization pattern depicted in FIGS. 11A-11B, for example,the fiducials are cross patterns 480 formed by a thin metallization linerunning perpendicular to and crossing a finger in the metallizationpattern. The thin metallization line may have a width of, for example,about 40 microns and may be similar or identical in width to the fingersit crosses. Alternatively, the fiducials may be, for example, filledcircles (for example, 600 micron diameter circles) or of any othersuitable shape and size. The fiducials may be formed from the samematerial (for example, silver) as the fingers. The fiducials may belocated, for example, at positions 485 around the perimeter of the frontsurface of the solar cell.

The bus bars, conductive fingers, and contact pads described above maybe formed, for example, from silver. Rear surface contact 455 may beformed, for example, from aluminum. Any other suitable materials mayalso be used for these structures.

Referring to the methods and solar cells described with respect to FIGS.4A-9, front surface bus bars (e.g., contact pad portions of such busbars) on standard size silicon solar cell wafers may have design widthsperpendicular to their long axes of, for example, about 1 mm to about1.5 mm with manufacturing tolerance of ±0.1 mm, resulting in real widthsof, for example, about 0.9 mm to about 1.6 mm. Rear surface bus bars(e.g., contact pad portions of such bus bars) may have design widthsperpendicular to their long axes of, for example, about 1.5 mm to about3.0 mm with manufacturing tolerance of about ±0.1 mm, resulting in realwidths of, for example, about 1.4 mm to about 3.1 mm.

In instances where a front surface bus bar partially overlies acorresponding rear surface bus bar on a standard sized silicon solarcell wafer, as per the method described with respect to FIGS. 4A-4C, thefront and rear surface bus bars may overlap in a direction perpendicularto their long axes by for example about 0 mm to about 1 mm, where at 0mm overlap the front and rear surface bus bars would be abutting if onthe same surface.

In the method described above with respect to FIGS. 4A-4C, each scribeline may be spaced apart from an edge of its corresponding front surfacebus bar by a predetermined distance of for example about 0.1 mm to about0.6 mm.

Shingled solar modules as described herein may be constructed asfollows, for example. As described above, standard size square or pseudosquare solar cells are diced to separate each standard solar cell intotwo or more rectangular or substantially rectangular solar cells. Therectangular or substantially rectangular solar cells are then arrangedin an overlapping manner and conductively bonded to each other to formsuper cells.

In a subsequent lay-up step, the super cells are arranged sunny sidedown on a transparent front sheet (e.g., a glass sheet) in the physicalconfiguration desired for the module. An encapsulant layer or sheet mayoptionally be positioned between the super cells and the transparentfront sheet. All leads, interconnects, and other conductors, if intendedto be present in the laminate structure of the finished solar module,are then arranged in the desired physical configuration with respect tothe super cells.

After the super cells and the other module components are arranged inthe desired physical configuration, a backing sheet is positioned on topof the arranged components. An encapsulant layer or sheet may optionallybe positioned between the backing sheet and the super cells. Theresulting structure is subjected to heat and pressure to form alaminate.

Any other method of constructing the solar modules described herein mayalso be used.

This disclosure is illustrative and not limiting. Further modificationswill be apparent to one skilled in the art in light of this disclosureand are intended to fall within the scope of the appended claims. Forexample, where methods and steps described above indicate certain eventsoccurring in certain order, those of ordinary skill in the art willrecognize that the ordering of certain steps may be modified, and thatsome steps may be omitted or additional steps added, and that suchmodifications are in accordance with the variations of the invention

1. (canceled)
 2. A solar module comprising: first and second siliconsolar cells, each comprising a front surface to be illuminated by light,an oppositely positioned rear surface, a first rear surface contact paddisposed on an edge of the rear surface, the first rear surface contactpad having an edge formed by a scribe line, and a front surface bus bardisposed on the front surface, the first and second silicon solar cellsarranged in a shingled manner with the front surface bus bar of thefirst silicon solar cell bonded to the first rear surface contact pad ofthe second silicon solar cell to electrically connect the first andsecond silicon solar cells in series.
 3. The solar module of claim 2,wherein the first and second silicon solar cells each comprise an edgeincluding a scribed edge portion and a cleaved edge portion thatcoincide with the scribe line.
 4. The solar module of claim 2, whereinthe front surface bus bar of the first silicon solar cell partially butnot entirely overlies the rear surface contact pad of the first siliconsolar cell.
 5. The solar module of claim 2, comprising a bonded areadefined by the area the front surface bus bar of the first silicon solarcell bonds to the rear surface contact pad of the second silicon solarcell, the bonded area having a short axis of a length of about 0.5 mm toabout 1.5 mm.
 6. The solar module of claim 3, wherein: the front andrear surfaces of the first silicon solar cell are square orpseudo-square in shape; a long axis of the rear surface contact pad ofthe first silicon solar cell is oriented parallel to the cleaved edge ofthe first silicon solar cell; and the rear surface contact pad of thefirst silicon solar cell extends for substantially the full length ofthe cleaved edge of the first silicon solar cell.
 7. The solar module ofclaim 2, wherein the first and second silicon solar cells each comprisea plurality of conductive fingers disposed on the front surface of thesilicon solar cells and electrically connected to their respective frontbus bars.
 8. The solar module of claim 2, wherein the second siliconsolar cell comprises a second rear surface contact pad having a longaxis parallel a long axis of the first silicon solar cell, the secondrear surface contact pad spaced apart from the first rear surfacecontact pad in a direction perpendicular to the long axis of the secondrear surface contact pad, the second rear surface contact pad bonded tothe front surface contact pad of the first silicon solar cell.
 9. Thesolar module of claim 2, wherein the edge formed by the scribe line is alaser cut edge.
 10. The solar module of claim 9, wherein the first andsecond silicon solar cells each comprise an edge including a laser cutedge portion and a cleaved edge portion that coincide with the scribeline.
 11. The solar module of claim 2, wherein the front surface bus barof the first silicon solar cell comprises a plurality of contact padsspaced apart and interconnected by a conductive line.
 12. The solarmodule of claim 11, wherein the plurality of contact pads of the frontsurface bus bar vary in size.
 13. The solar module of claim 2, whereinthe front and rear surfaces of the first silicon solar cell have arectangle shape and the edge formed by the scribe line is parallel to along axis of the first silicon solar cell.
 14. A solar modulecomprising: a plurality of super cells, each super cell comprising:first and second silicon solar cells, each comprising a front surface tobe illuminated by light, an oppositely positioned rear surface, a firstrear surface contact pad disposed on an edge of the rear surface, thefirst rear surface contact pad having an edge formed by a scribe line,and a front surface bus bar disposed on the front surface, the first andsecond silicon solar cells arranged in a shingled manner with the frontsurface bus bar of the first silicon solar cell bonded to the first rearsurface contact pad of the second silicon solar cell to electricallyconnect of the first and second silicon solar cells in series.
 15. Thesolar module of claim 14, wherein the first and second silicon solarcells each comprise an edge including a scribed edge portion and acleaved edge portion that coincide with the scribe line.
 16. The solarmodule of claim 14, wherein the front surface bus bar of the firstsilicon solar cells partially but not entirely overlies the rear surfacecontact pad of the first silicon solar cells.
 17. The solar module ofclaim 14, comprising a bonded area defined by the area the front surfacebus bar of the first silicon solar cells bonds to the rear surfacecontact pad of the second silicon solar cells, each bonded area having ashort axis of a length of about 0.5 mm to about 1.5 mm.
 18. The solarmodule of claim 14, wherein the second silicon solar cell comprises asecond rear surface contact pad having a long axis parallel a long axisof the first silicon solar cell, the second rear surface contact padspaced apart from the first rear surface contact pad in a directionperpendicular to the long axis of the second rear surface contact pad,the second rear surface contact pad bonded to the front surface bus barof the first silicon solar cell.
 19. The solar module of claim 14,wherein the edge formed by the scribe line is a laser cut edge.
 20. Thesolar module of claim 19, wherein the first and second silicon solarcells each comprise an edge including a laser cut edge portion and acleaved edge portion that coincide with the scribe line.
 21. The solarmodule of claim 14, wherein the front surface bus bar of the firstsilicon solar cell comprises a plurality of contact pads spaced apartand interconnected by a conductive line.